// SPDX-License-Identifier: GPL-2.0
/*
* Common Block IO controller cgroup interface
*
* Based on ideas and code from CFQ, CFS and BFQ:
* Copyright (C) 2003 Jens Axboe <[email protected]>
*
* Copyright (C) 2008 Fabio Checconi <[email protected]>
* Paolo Valente <[email protected]>
*
* Copyright (C) 2009 Vivek Goyal <[email protected]>
* Nauman Rafique <[email protected]>
*
* For policy-specific per-blkcg data:
* Copyright (C) 2015 Paolo Valente <[email protected]>
* Arianna Avanzini <[email protected]>
*/
#include <linux/ioprio.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/sched/signal.h>
#include <linux/err.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/atomic.h>
#include <linux/ctype.h>
#include <linux/resume_user_mode.h>
#include <linux/psi.h>
#include <linux/part_stat.h>
#include "blk.h"
#include "blk-cgroup.h"
#include "blk-ioprio.h"
#include "blk-throttle.h"
static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu);
/*
* blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
* blkcg_pol_register_mutex nests outside of it and synchronizes entire
* policy [un]register operations including cgroup file additions /
* removals. Putting cgroup file registration outside blkcg_pol_mutex
* allows grabbing it from cgroup callbacks.
*/
static DEFINE_MUTEX(blkcg_pol_register_mutex);
static DEFINE_MUTEX(blkcg_pol_mutex);
struct blkcg blkcg_root;
EXPORT_SYMBOL_GPL(blkcg_root);
struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
EXPORT_SYMBOL_GPL(blkcg_root_css);
static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
bool blkcg_debug_stats = false;
static DEFINE_RAW_SPINLOCK(blkg_stat_lock);
#define BLKG_DESTROY_BATCH_SIZE 64
/*
* Lockless lists for tracking IO stats update
*
* New IO stats are stored in the percpu iostat_cpu within blkcg_gq (blkg).
* There are multiple blkg's (one for each block device) attached to each
* blkcg. The rstat code keeps track of which cpu has IO stats updated,
* but it doesn't know which blkg has the updated stats. If there are many
* block devices in a system, the cost of iterating all the blkg's to flush
* out the IO stats can be high. To reduce such overhead, a set of percpu
* lockless lists (lhead) per blkcg are used to track the set of recently
* updated iostat_cpu's since the last flush. An iostat_cpu will be put
* onto the lockless list on the update side [blk_cgroup_bio_start()] if
* not there yet and then removed when being flushed [blkcg_rstat_flush()].
* References to blkg are gotten and then put back in the process to
* protect against blkg removal.
*
* Return: 0 if successful or -ENOMEM if allocation fails.
*/
static int init_blkcg_llists(struct blkcg *blkcg)
{
int cpu;
blkcg->lhead = alloc_percpu_gfp(struct llist_head, GFP_KERNEL);
if (!blkcg->lhead)
return -ENOMEM;
for_each_possible_cpu(cpu)
init_llist_head(per_cpu_ptr(blkcg->lhead, cpu));
return 0;
}
/**
* blkcg_css - find the current css
*
* Find the css associated with either the kthread or the current task.
* This may return a dying css, so it is up to the caller to use tryget logic
* to confirm it is alive and well.
*/
static struct cgroup_subsys_state *blkcg_css(void)
{
struct cgroup_subsys_state *css;
css = kthread_blkcg();
if (css)
return css;
return task_css(current, io_cgrp_id);
}
static bool blkcg_policy_enabled(struct request_queue *q,
const struct blkcg_policy *pol)
{
return pol && test_bit(pol->plid, q->blkcg_pols);
}
static void blkg_free_workfn(struct work_struct *work)
{
struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
free_work);
struct request_queue *q = blkg->q;
int i;
/*
* pd_free_fn() can also be called from blkcg_deactivate_policy(),
* in order to make sure pd_free_fn() is called in order, the deletion
* of the list blkg->q_node is delayed to here from blkg_destroy(), and
* blkcg_mutex is used to synchronize blkg_free_workfn() and
* blkcg_deactivate_policy().
*/
mutex_lock(&q->blkcg_mutex);
for (i = 0; i < BLKCG_MAX_POLS; i++)
if (blkg->pd[i])
blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
if (blkg->parent)
blkg_put(blkg->parent);
spin_lock_irq(&q->queue_lock);
list_del_init(&blkg->q_node);
spin_unlock_irq(&q->queue_lock);
mutex_unlock(&q->blkcg_mutex);
blk_put_queue(q);
free_percpu(blkg->iostat_cpu);
percpu_ref_exit(&blkg->refcnt);
kfree(blkg);
}
/**
* blkg_free - free a blkg
* @blkg: blkg to free
*
* Free @blkg which may be partially allocated.
*/
static void blkg_free(struct blkcg_gq *blkg)
{
if (!blkg)
return;
/*
* Both ->pd_free_fn() and request queue's release handler may
* sleep, so free us by scheduling one work func
*/
INIT_WORK(&blkg->free_work, blkg_free_workfn);
schedule_work(&blkg->free_work);
}
static void __blkg_release(struct rcu_head *rcu)
{
struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
struct blkcg *blkcg = blkg->blkcg;
int cpu;
#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
WARN_ON(!bio_list_empty(&blkg->async_bios));
#endif
/*
* Flush all the non-empty percpu lockless lists before releasing
* us, given these stat belongs to us.
*
* blkg_stat_lock is for serializing blkg stat update
*/
for_each_possible_cpu(cpu)
__blkcg_rstat_flush(blkcg, cpu);
/* release the blkcg and parent blkg refs this blkg has been holding */
css_put(&blkg->blkcg->css);
blkg_free(blkg);
}
/*
* A group is RCU protected, but having an rcu lock does not mean that one
* can access all the fields of blkg and assume these are valid. For
* example, don't try to follow throtl_data and request queue links.
*
* Having a reference to blkg under an rcu allows accesses to only values
* local to groups like group stats and group rate limits.
*/
static void blkg_release(struct percpu_ref *ref)
{
struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
call_rcu(&blkg->rcu_head, __blkg_release);
}
#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
static struct workqueue_struct *blkcg_punt_bio_wq;
static void blkg_async_bio_workfn(struct work_struct *work)
{
struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
async_bio_work);
struct bio_list bios = BIO_EMPTY_LIST;
struct bio *bio;
struct blk_plug plug;
bool need_plug = false;
/* as long as there are pending bios, @blkg can't go away */
spin_lock(&blkg->async_bio_lock);
bio_list_merge_init(&bios, &blkg->async_bios);
spin_unlock(&blkg->async_bio_lock);
/* start plug only when bio_list contains at least 2 bios */
if (bios.head && bios.head->bi_next) {
need_plug = true;
blk_start_plug(&plug);
}
while ((bio = bio_list_pop(&bios)))
submit_bio(bio);
if (need_plug)
blk_finish_plug(&plug);
}
/*
* When a shared kthread issues a bio for a cgroup, doing so synchronously can
* lead to priority inversions as the kthread can be trapped waiting for that
* cgroup. Use this helper instead of submit_bio to punt the actual issuing to
* a dedicated per-blkcg work item to avoid such priority inversions.
*/
void blkcg_punt_bio_submit(struct bio *bio)
{
struct blkcg_gq *blkg = bio->bi_blkg;
if (blkg->parent) {
spin_lock(&blkg->async_bio_lock);
bio_list_add(&blkg->async_bios, bio);
spin_unlock(&blkg->async_bio_lock);
queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
} else {
/* never bounce for the root cgroup */
submit_bio(bio);
}
}
EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);
static int __init blkcg_punt_bio_init(void)
{
blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
WQ_MEM_RECLAIM | WQ_FREEZABLE |
WQ_UNBOUND | WQ_SYSFS, 0);
if (!blkcg_punt_bio_wq)
return -ENOMEM;
return 0;
}
subsys_initcall(blkcg_punt_bio_init);
#endif /* CONFIG_BLK_CGROUP_PUNT_BIO */
/**
* bio_blkcg_css - return the blkcg CSS associated with a bio
* @bio: target bio
*
* This returns the CSS for the blkcg associated with a bio, or %NULL if not
* associated. Callers are expected to either handle %NULL or know association
* has been done prior to calling this.
*/
struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
{
if (!bio || !bio->bi_blkg)
return NULL;
return &bio->bi_blkg->blkcg->css;
}
EXPORT_SYMBOL_GPL(bio_blkcg_css);
/**
* blkcg_parent - get the parent of a blkcg
* @blkcg: blkcg of interest
*
* Return the parent blkcg of @blkcg. Can be called anytime.
*/
static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
{
return css_to_blkcg(blkcg->css.parent);
}
/**
* blkg_alloc - allocate a blkg
* @blkcg: block cgroup the new blkg is associated with
* @disk: gendisk the new blkg is associated with
* @gfp_mask: allocation mask to use
*
* Allocate a new blkg associating @blkcg and @disk.
*/
static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
gfp_t gfp_mask)
{
struct blkcg_gq *blkg;
int i, cpu;
/* alloc and init base part */
blkg = kzalloc_node(sizeof(*blkg), gfp_mask, disk->queue->node);
if (!blkg)
return NULL;
if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
goto out_free_blkg;
blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
if (!blkg->iostat_cpu)
goto out_exit_refcnt;
if (!blk_get_queue(disk->queue))
goto out_free_iostat;
blkg->q = disk->queue;
INIT_LIST_HEAD(&blkg->q_node);
blkg->blkcg = blkcg;
blkg->iostat.blkg = blkg;
#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
spin_lock_init(&blkg->async_bio_lock);
bio_list_init(&blkg->async_bios);
INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
#endif
u64_stats_init(&blkg->iostat.sync);
for_each_possible_cpu(cpu) {
u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync);
per_cpu_ptr(blkg->iostat_cpu, cpu)->blkg = blkg;
}
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
struct blkg_policy_data *pd;
if (!blkcg_policy_enabled(disk->queue, pol))
continue;
/* alloc per-policy data and attach it to blkg */
pd = pol->pd_alloc_fn(disk, blkcg, gfp_mask);
if (!pd)
goto out_free_pds;
blkg->pd[i] = pd;
pd->blkg = blkg;
pd->plid = i;
pd->online = false;
}
return blkg;
out_free_pds:
while (--i >= 0)
if (blkg->pd[i])
blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
blk_put_queue(disk->queue);
out_free_iostat:
free_percpu(blkg->iostat_cpu);
out_exit_refcnt:
percpu_ref_exit(&blkg->refcnt);
out_free_blkg:
kfree(blkg);
return NULL;
}
/*
* If @new_blkg is %NULL, this function tries to allocate a new one as
* necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
*/
static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk,
struct blkcg_gq *new_blkg)
{
struct blkcg_gq *blkg;
int i, ret;
lockdep_assert_held(&disk->queue->queue_lock);
/* request_queue is dying, do not create/recreate a blkg */
if (blk_queue_dying(disk->queue)) {
ret = -ENODEV;
goto err_free_blkg;
}
/* blkg holds a reference to blkcg */
if (!css_tryget_online(&blkcg->css)) {
ret = -ENODEV;
goto err_free_blkg;
}
/* allocate */
if (!new_blkg) {
new_blkg = blkg_alloc(blkcg, disk, GFP_NOWAIT | __GFP_NOWARN);
if (unlikely(!new_blkg)) {
ret = -ENOMEM;
goto err_put_css;
}
}
blkg = new_blkg;
/* link parent */
if (blkcg_parent(blkcg)) {
blkg->parent = blkg_lookup(blkcg_parent(blkcg), disk->queue);
if (WARN_ON_ONCE(!blkg->parent)) {
ret = -ENODEV;
goto err_put_css;
}
blkg_get(blkg->parent);
}
/* invoke per-policy init */
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (blkg->pd[i] && pol->pd_init_fn)
pol->pd_init_fn(blkg->pd[i]);
}
/* insert */
spin_lock(&blkcg->lock);
ret = radix_tree_insert(&blkcg->blkg_tree, disk->queue->id, blkg);
if (likely(!ret)) {
hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
list_add(&blkg->q_node, &disk->queue->blkg_list);
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (blkg->pd[i]) {
if (pol->pd_online_fn)
pol->pd_online_fn(blkg->pd[i]);
blkg->pd[i]->online = true;
}
}
}
blkg->online = true;
spin_unlock(&blkcg->lock);
if (!ret)
return blkg;
/* @blkg failed fully initialized, use the usual release path */
blkg_put(blkg);
return ERR_PTR(ret);
err_put_css:
css_put(&blkcg->css);
err_free_blkg:
if (new_blkg)
blkg_free(new_blkg);
return ERR_PTR(ret);
}
/**
* blkg_lookup_create - lookup blkg, try to create one if not there
* @blkcg: blkcg of interest
* @disk: gendisk of interest
*
* Lookup blkg for the @blkcg - @disk pair. If it doesn't exist, try to
* create one. blkg creation is performed recursively from blkcg_root such
* that all non-root blkg's have access to the parent blkg. This function
* should be called under RCU read lock and takes @disk->queue->queue_lock.
*
* Returns the blkg or the closest blkg if blkg_create() fails as it walks
* down from root.
*/
static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct blkcg_gq *blkg;
unsigned long flags;
WARN_ON_ONCE(!rcu_read_lock_held());
blkg = blkg_lookup(blkcg, q);
if (blkg)
return blkg;
spin_lock_irqsave(&q->queue_lock, flags);
blkg = blkg_lookup(blkcg, q);
if (blkg) {
if (blkcg != &blkcg_root &&
blkg != rcu_dereference(blkcg->blkg_hint))
rcu_assign_pointer(blkcg->blkg_hint, blkg);
goto found;
}
/*
* Create blkgs walking down from blkcg_root to @blkcg, so that all
* non-root blkgs have access to their parents. Returns the closest
* blkg to the intended blkg should blkg_create() fail.
*/
while (true) {
struct blkcg *pos = blkcg;
struct blkcg *parent = blkcg_parent(blkcg);
struct blkcg_gq *ret_blkg = q->root_blkg;
while (parent) {
blkg = blkg_lookup(parent, q);
if (blkg) {
/* remember closest blkg */
ret_blkg = blkg;
break;
}
pos = parent;
parent = blkcg_parent(parent);
}
blkg = blkg_create(pos, disk, NULL);
if (IS_ERR(blkg)) {
blkg = ret_blkg;
break;
}
if (pos == blkcg)
break;
}
found:
spin_unlock_irqrestore(&q->queue_lock, flags);
return blkg;
}
static void blkg_destroy(struct blkcg_gq *blkg)
{
struct blkcg *blkcg = blkg->blkcg;
int i;
lockdep_assert_held(&blkg->q->queue_lock);
lockdep_assert_held(&blkcg->lock);
/*
* blkg stays on the queue list until blkg_free_workfn(), see details in
* blkg_free_workfn(), hence this function can be called from
* blkcg_destroy_blkgs() first and again from blkg_destroy_all() before
* blkg_free_workfn().
*/
if (hlist_unhashed(&blkg->blkcg_node))
return;
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (blkg->pd[i] && blkg->pd[i]->online) {
blkg->pd[i]->online = false;
if (pol->pd_offline_fn)
pol->pd_offline_fn(blkg->pd[i]);
}
}
blkg->online = false;
radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
hlist_del_init_rcu(&blkg->blkcg_node);
/*
* Both setting lookup hint to and clearing it from @blkg are done
* under queue_lock. If it's not pointing to @blkg now, it never
* will. Hint assignment itself can race safely.
*/
if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
rcu_assign_pointer(blkcg->blkg_hint, NULL);
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
percpu_ref_kill(&blkg->refcnt);
}
static void blkg_destroy_all(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct blkcg_gq *blkg;
int count = BLKG_DESTROY_BATCH_SIZE;
int i;
restart:
spin_lock_irq(&q->queue_lock);
list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;
if (hlist_unhashed(&blkg->blkcg_node))
continue;
spin_lock(&blkcg->lock);
blkg_destroy(blkg);
spin_unlock(&blkcg->lock);
/*
* in order to avoid holding the spin lock for too long, release
* it when a batch of blkgs are destroyed.
*/
if (!(--count)) {
count = BLKG_DESTROY_BATCH_SIZE;
spin_unlock_irq(&q->queue_lock);
cond_resched();
goto restart;
}
}
/*
* Mark policy deactivated since policy offline has been done, and
* the free is scheduled, so future blkcg_deactivate_policy() can
* be bypassed
*/
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (pol)
__clear_bit(pol->plid, q->blkcg_pols);
}
q->root_blkg = NULL;
spin_unlock_irq(&q->queue_lock);
}
static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)
{
int i;
for (i = 0; i < BLKG_IOSTAT_NR; i++) {
dst->bytes[i] = src->bytes[i];
dst->ios[i] = src->ios[i];
}
}
static void __blkg_clear_stat(struct blkg_iostat_set *bis)
{
struct blkg_iostat cur = {0};
unsigned long flags;
flags = u64_stats_update_begin_irqsave(&bis->sync);
blkg_iostat_set(&bis->cur, &cur);
blkg_iostat_set(&bis->last, &cur);
u64_stats_update_end_irqrestore(&bis->sync, flags);
}
static void blkg_clear_stat(struct blkcg_gq *blkg)
{
int cpu;
for_each_possible_cpu(cpu) {
struct blkg_iostat_set *s = per_cpu_ptr(blkg->iostat_cpu, cpu);
__blkg_clear_stat(s);
}
__blkg_clear_stat(&blkg->iostat);
}
static int blkcg_reset_stats(struct cgroup_subsys_state *css,
struct cftype *cftype, u64 val)
{
struct blkcg *blkcg = css_to_blkcg(css);
struct blkcg_gq *blkg;
int i;
mutex_lock(&blkcg_pol_mutex);
spin_lock_irq(&blkcg->lock);
/*
* Note that stat reset is racy - it doesn't synchronize against
* stat updates. This is a debug feature which shouldn't exist
* anyway. If you get hit by a race, retry.
*/
hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
blkg_clear_stat(blkg);
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (blkg->pd[i] && pol->pd_reset_stats_fn)
pol->pd_reset_stats_fn(blkg->pd[i]);
}
}
spin_unlock_irq(&blkcg->lock);
mutex_unlock(&blkcg_pol_mutex);
return 0;
}
const char *blkg_dev_name(struct blkcg_gq *blkg)
{
if (!blkg->q->disk)
return NULL;
return bdi_dev_name(blkg->q->disk->bdi);
}
/**
* blkcg_print_blkgs - helper for printing per-blkg data
* @sf: seq_file to print to
* @blkcg: blkcg of interest
* @prfill: fill function to print out a blkg
* @pol: policy in question
* @data: data to be passed to @prfill
* @show_total: to print out sum of prfill return values or not
*
* This function invokes @prfill on each blkg of @blkcg if pd for the
* policy specified by @pol exists. @prfill is invoked with @sf, the
* policy data and @data and the matching queue lock held. If @show_total
* is %true, the sum of the return values from @prfill is printed with
* "Total" label at the end.
*
* This is to be used to construct print functions for
* cftype->read_seq_string method.
*/
void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
u64 (*prfill)(struct seq_file *,
struct blkg_policy_data *, int),
const struct blkcg_policy *pol, int data,
bool show_total)
{
struct blkcg_gq *blkg;
u64 total = 0;
rcu_read_lock();
hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
spin_lock_irq(&blkg->q->queue_lock);
if (blkcg_policy_enabled(blkg->q, pol))
total += prfill(sf, blkg->pd[pol->plid], data);
spin_unlock_irq(&blkg->q->queue_lock);
}
rcu_read_unlock();
if (show_total)
seq_printf(sf, "Total %llu\n", (unsigned long long)total);
}
EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
/**
* __blkg_prfill_u64 - prfill helper for a single u64 value
* @sf: seq_file to print to
* @pd: policy private data of interest
* @v: value to print
*
* Print @v to @sf for the device associated with @pd.
*/
u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
{
const char *dname = blkg_dev_name(pd->blkg);
if (!dname)
return 0;
seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
return v;
}
EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
/**
* blkg_conf_init - initialize a blkg_conf_ctx
* @ctx: blkg_conf_ctx to initialize
* @input: input string
*
* Initialize @ctx which can be used to parse blkg config input string @input.
* Once initialized, @ctx can be used with blkg_conf_open_bdev() and
* blkg_conf_prep(), and must be cleaned up with blkg_conf_exit().
*/
void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input)
{
*ctx = (struct blkg_conf_ctx){ .input = input };
}
EXPORT_SYMBOL_GPL(blkg_conf_init);
/**
* blkg_conf_open_bdev - parse and open bdev for per-blkg config update
* @ctx: blkg_conf_ctx initialized with blkg_conf_init()
*
* Parse the device node prefix part, MAJ:MIN, of per-blkg config update from
* @ctx->input and get and store the matching bdev in @ctx->bdev. @ctx->body is
* set to point past the device node prefix.
*
* This function may be called multiple times on @ctx and the extra calls become
* NOOPs. blkg_conf_prep() implicitly calls this function. Use this function
* explicitly if bdev access is needed without resolving the blkcg / policy part
* of @ctx->input. Returns -errno on error.
*/
int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx)
{
char *input = ctx->input;
unsigned int major, minor;
struct block_device *bdev;
int key_len;
if (ctx->bdev)
return 0;
if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
return -EINVAL;
input += key_len;
if (!isspace(*input))
return -EINVAL;
input = skip_spaces(input);
bdev = blkdev_get_no_open(MKDEV(major, minor));
if (!bdev)
return -ENODEV;
if (bdev_is_partition(bdev)) {
blkdev_put_no_open(bdev);
return -ENODEV;
}
mutex_lock(&bdev->bd_queue->rq_qos_mutex);
if (!disk_live(bdev->bd_disk)) {
blkdev_put_no_open(bdev);
mutex_unlock(&bdev->bd_queue->rq_qos_mutex);
return -ENODEV;
}
ctx->body = input;
ctx->bdev = bdev;
return 0;
}
/**
* blkg_conf_prep - parse and prepare for per-blkg config update
* @blkcg: target block cgroup
* @pol: target policy
* @ctx: blkg_conf_ctx initialized with blkg_conf_init()
*
* Parse per-blkg config update from @ctx->input and initialize @ctx
* accordingly. On success, @ctx->body points to the part of @ctx->input
* following MAJ:MIN, @ctx->bdev points to the target block device and
* @ctx->blkg to the blkg being configured.
*
* blkg_conf_open_bdev() may be called on @ctx beforehand. On success, this
* function returns with queue lock held and must be followed by
* blkg_conf_exit().
*/
int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
struct blkg_conf_ctx *ctx)
__acquires(&bdev->bd_queue->queue_lock)
{
struct gendisk *disk;
struct request_queue *q;
struct blkcg_gq *blkg;
int ret;
ret = blkg_conf_open_bdev(ctx);
if (ret)
return ret;
disk = ctx->bdev->bd_disk;
q = disk->queue;
/*
* blkcg_deactivate_policy() requires queue to be frozen, we can grab
* q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
*/
ret = blk_queue_enter(q, 0);
if (ret)
goto fail;
spin_lock_irq(&q->queue_lock);
if (!blkcg_policy_enabled(q, pol)) {
ret = -EOPNOTSUPP;
goto fail_unlock;
}
blkg = blkg_lookup(blkcg, q);
if (blkg)
goto success;
/*
* Create blkgs walking down from blkcg_root to @blkcg, so that all
* non-root blkgs have access to their parents.
*/
while (true) {
struct blkcg *pos = blkcg;
struct blkcg *parent;
struct blkcg_gq *new_blkg;
parent = blkcg_parent(blkcg);
while (parent && !blkg_lookup(parent, q)) {
pos = parent;
parent = blkcg_parent(parent);
}
/* Drop locks to do new blkg allocation with GFP_KERNEL. */
spin_unlock_irq(&q->queue_lock);
new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);
if (unlikely(!new_blkg)) {
ret = -ENOMEM;
goto fail_exit_queue;
}
if (radix_tree_preload(GFP_KERNEL)) {
blkg_free(new_blkg);
ret = -ENOMEM;
goto fail_exit_queue;
}
spin_lock_irq(&q->queue_lock);
if (!blkcg_policy_enabled(q, pol)) {
blkg_free(new_blkg);
ret = -EOPNOTSUPP;
goto fail_preloaded;
}
blkg = blkg_lookup(pos, q);
if (blkg) {
blkg_free(new_blkg);
} else {
blkg = blkg_create(pos, disk, new_blkg);
if (IS_ERR(blkg)) {
ret = PTR_ERR(blkg);
goto fail_preloaded;
}
}
radix_tree_preload_end();
if (pos == blkcg)
goto success;
}
success:
blk_queue_exit(q);
ctx->blkg = blkg;
return 0;
fail_preloaded:
radix_tree_preload_end();
fail_unlock:
spin_unlock_irq(&q->queue_lock);
fail_exit_queue:
blk_queue_exit(q);
fail:
/*
* If queue was bypassing, we should retry. Do so after a
* short msleep(). It isn't strictly necessary but queue
* can be bypassing for some time and it's always nice to
* avoid busy looping.
*/
if (ret == -EBUSY) {
msleep(10);
ret = restart_syscall();
}
return ret;
}
EXPORT_SYMBOL_GPL(blkg_conf_prep);
/**
* blkg_conf_exit - clean up per-blkg config update
* @ctx: blkg_conf_ctx initialized with blkg_conf_init()
*
* Clean up after per-blkg config update. This function must be called on all
* blkg_conf_ctx's initialized with blkg_conf_init().
*/
void blkg_conf_exit(struct blkg_conf_ctx *ctx)
__releases(&ctx->bdev->bd_queue->queue_lock)
__releases(&ctx->bdev->bd_queue->rq_qos_mutex)
{
if (ctx->blkg) {
spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
ctx->blkg = NULL;
}
if (ctx->bdev) {
mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex);
blkdev_put_no_open(ctx->bdev);
ctx->body = NULL;
ctx->bdev = NULL;
}
}
EXPORT_SYMBOL_GPL(blkg_conf_exit);
static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
{
int i;
for (i = 0; i < BLKG_IOSTAT_NR; i++) {
dst->bytes[i] += src->bytes[i];
dst->ios[i] += src->ios[i];
}
}
static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src)
{
int i;
for (i = 0; i < BLKG_IOSTAT_NR; i++) {
dst->bytes[i] -= src->bytes[i];
dst->ios[i] -= src->ios[i];
}
}
static void blkcg_iostat_update(struct blkcg_gq *blkg, struct blkg_iostat *cur,
struct blkg_iostat *last)
{
struct blkg_iostat delta;
unsigned long flags;
/* propagate percpu delta to global */
flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
blkg_iostat_set(&delta, cur);
blkg_iostat_sub(&delta, last);
blkg_iostat_add(&blkg->iostat.cur, &delta);
blkg_iostat_add(last, &delta);
u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
}
static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu)
{
struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu);
struct llist_node *lnode;
struct blkg_iostat_set *bisc, *next_bisc;
unsigned long flags;
rcu_read_lock();
lnode = llist_del_all(lhead);
if (!lnode)
goto out;
/*
* For covering concurrent parent blkg update from blkg_release().
*
* When flushing from cgroup, cgroup_rstat_lock is always held, so
* this lock won't cause contention most of time.
*/
raw_spin_lock_irqsave(&blkg_stat_lock, flags);
/*
* Iterate only the iostat_cpu's queued in the lockless list.
*/
llist_for_each_entry_safe(bisc, next_bisc, lnode, lnode) {
struct blkcg_gq *blkg = bisc->blkg;
struct blkcg_gq *parent = blkg->parent;
struct blkg_iostat cur;
unsigned int seq;
/*
* Order assignment of `next_bisc` from `bisc->lnode.next` in
* llist_for_each_entry_safe and clearing `bisc->lqueued` for
* avoiding to assign `next_bisc` with new next pointer added
* in blk_cgroup_bio_start() in case of re-ordering.
*
* The pair barrier is implied in llist_add() in blk_cgroup_bio_start().
*/
smp_mb();
WRITE_ONCE(bisc->lqueued, false);
if (bisc == &blkg->iostat)
goto propagate_up; /* propagate up to parent only */
/* fetch the current per-cpu values */
do {
seq = u64_stats_fetch_begin(&bisc->sync);
blkg_iostat_set(&cur, &bisc->cur);
} while (u64_stats_fetch_retry(&bisc->sync, seq));
blkcg_iostat_update(blkg, &cur, &bisc->last);
propagate_up:
/* propagate global delta to parent (unless that's root) */
if (parent && parent->parent) {
blkcg_iostat_update(parent, &blkg->iostat.cur,
&blkg->iostat.last);
/*
* Queue parent->iostat to its blkcg's lockless
* list to propagate up to the grandparent if the
* iostat hasn't been queued yet.
*/
if (!parent->iostat.lqueued) {
struct llist_head *plhead;
plhead = per_cpu_ptr(parent->blkcg->lhead, cpu);
llist_add(&parent->iostat.lnode, plhead);
parent->iostat.lqueued = true;
}
}
}
raw_spin_unlock_irqrestore(&blkg_stat_lock, flags);
out:
rcu_read_unlock();
}
static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
{
/* Root-level stats are sourced from system-wide IO stats */
if (cgroup_parent(css->cgroup))
__blkcg_rstat_flush(css_to_blkcg(css), cpu);
}
/*
* We source root cgroup stats from the system-wide stats to avoid
* tracking the same information twice and incurring overhead when no
* cgroups are defined. For that reason, cgroup_rstat_flush in
* blkcg_print_stat does not actually fill out the iostat in the root
* cgroup's blkcg_gq.
*
* However, we would like to re-use the printing code between the root and
* non-root cgroups to the extent possible. For that reason, we simulate
* flushing the root cgroup's stats by explicitly filling in the iostat
* with disk level statistics.
*/
static void blkcg_fill_root_iostats(void)
{
struct class_dev_iter iter;
struct device *dev;
class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
while ((dev = class_dev_iter_next(&iter))) {
struct block_device *bdev = dev_to_bdev(dev);
struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg;
struct blkg_iostat tmp;
int cpu;
unsigned long flags;
memset(&tmp, 0, sizeof(tmp));
for_each_possible_cpu(cpu) {
struct disk_stats *cpu_dkstats;
cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
tmp.ios[BLKG_IOSTAT_READ] +=
cpu_dkstats->ios[STAT_READ];
tmp.ios[BLKG_IOSTAT_WRITE] +=
cpu_dkstats->ios[STAT_WRITE];
tmp.ios[BLKG_IOSTAT_DISCARD] +=
cpu_dkstats->ios[STAT_DISCARD];
// convert sectors to bytes
tmp.bytes[BLKG_IOSTAT_READ] +=
cpu_dkstats->sectors[STAT_READ] << 9;
tmp.bytes[BLKG_IOSTAT_WRITE] +=
cpu_dkstats->sectors[STAT_WRITE] << 9;
tmp.bytes[BLKG_IOSTAT_DISCARD] +=
cpu_dkstats->sectors[STAT_DISCARD] << 9;
}
flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
blkg_iostat_set(&blkg->iostat.cur, &tmp);
u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
}
}
static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
{
struct blkg_iostat_set *bis = &blkg->iostat;
u64 rbytes, wbytes, rios, wios, dbytes, dios;
const char *dname;
unsigned seq;
int i;
if (!blkg->online)
return;
dname = blkg_dev_name(blkg);
if (!dname)
return;
seq_printf(s, "%s ", dname);
do {
seq = u64_stats_fetch_begin(&bis->sync);
rbytes = bis->cur.bytes[BLKG_IOSTAT_READ];
wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE];
dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD];
rios = bis->cur.ios[BLKG_IOSTAT_READ];
wios = bis->cur.ios[BLKG_IOSTAT_WRITE];
dios = bis->cur.ios[BLKG_IOSTAT_DISCARD];
} while (u64_stats_fetch_retry(&bis->sync, seq));
if (rbytes || wbytes || rios || wios) {
seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
rbytes, wbytes, rios, wios,
dbytes, dios);
}
if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
seq_printf(s, " use_delay=%d delay_nsec=%llu",
atomic_read(&blkg->use_delay),
atomic64_read(&blkg->delay_nsec));
}
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
if (!blkg->pd[i] || !pol->pd_stat_fn)
continue;
pol->pd_stat_fn(blkg->pd[i], s);
}
seq_puts(s, "\n");
}
static int blkcg_print_stat(struct seq_file *sf, void *v)
{
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
struct blkcg_gq *blkg;
if (!seq_css(sf)->parent)
blkcg_fill_root_iostats();
else
cgroup_rstat_flush(blkcg->css.cgroup);
rcu_read_lock();
hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
spin_lock_irq(&blkg->q->queue_lock);
blkcg_print_one_stat(blkg, sf);
spin_unlock_irq(&blkg->q->queue_lock);
}
rcu_read_unlock();
return 0;
}
static struct cftype blkcg_files[] = {
{
.name = "stat",
.seq_show = blkcg_print_stat,
},
{ } /* terminate */
};
static struct cftype blkcg_legacy_files[] = {
{
.name = "reset_stats",
.write_u64 = blkcg_reset_stats,
},
{ } /* terminate */
};
#ifdef CONFIG_CGROUP_WRITEBACK
struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css)
{
return &css_to_blkcg(css)->cgwb_list;
}
#endif
/*
* blkcg destruction is a three-stage process.
*
* 1. Destruction starts. The blkcg_css_offline() callback is invoked
* which offlines writeback. Here we tie the next stage of blkg destruction
* to the completion of writeback associated with the blkcg. This lets us
* avoid punting potentially large amounts of outstanding writeback to root
* while maintaining any ongoing policies. The next stage is triggered when
* the nr_cgwbs count goes to zero.
*
* 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
* and handles the destruction of blkgs. Here the css reference held by
* the blkg is put back eventually allowing blkcg_css_free() to be called.
* This work may occur in cgwb_release_workfn() on the cgwb_release
* workqueue. Any submitted ios that fail to get the blkg ref will be
* punted to the root_blkg.
*
* 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
* This finally frees the blkcg.
*/
/**
* blkcg_destroy_blkgs - responsible for shooting down blkgs
* @blkcg: blkcg of interest
*
* blkgs should be removed while holding both q and blkcg locks. As blkcg lock
* is nested inside q lock, this function performs reverse double lock dancing.
* Destroying the blkgs releases the reference held on the blkcg's css allowing
* blkcg_css_free to eventually be called.
*
* This is the blkcg counterpart of ioc_release_fn().
*/
static void blkcg_destroy_blkgs(struct blkcg *blkcg)
{
might_sleep();
spin_lock_irq(&blkcg->lock);
while (!hlist_empty(&blkcg->blkg_list)) {
struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
struct blkcg_gq, blkcg_node);
struct request_queue *q = blkg->q;
if (need_resched() || !spin_trylock(&q->queue_lock)) {
/*
* Given that the system can accumulate a huge number
* of blkgs in pathological cases, check to see if we
* need to rescheduling to avoid softlockup.
*/
spin_unlock_irq(&blkcg->lock);
cond_resched();
spin_lock_irq(&blkcg->lock);
continue;
}
blkg_destroy(blkg);
spin_unlock(&q->queue_lock);
}
spin_unlock_irq(&blkcg->lock);
}
/**
* blkcg_pin_online - pin online state
* @blkcg_css: blkcg of interest
*
* While pinned, a blkcg is kept online. This is primarily used to
* impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
* while an associated cgwb is still active.
*/
void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css)
{
refcount_inc(&css_to_blkcg(blkcg_css)->online_pin);
}
/**
* blkcg_unpin_online - unpin online state
* @blkcg_css: blkcg of interest
*
* This is primarily used to impedance-match blkg and cgwb lifetimes so
* that blkg doesn't go offline while an associated cgwb is still active.
* When this count goes to zero, all active cgwbs have finished so the
* blkcg can continue destruction by calling blkcg_destroy_blkgs().
*/
void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
{
struct blkcg *blkcg = css_to_blkcg(blkcg_css);
do {
if (!refcount_dec_and_test(&blkcg->online_pin))
break;
blkcg_destroy_blkgs(blkcg);
blkcg = blkcg_parent(blkcg);
} while (blkcg);
}
/**
* blkcg_css_offline - cgroup css_offline callback
* @css: css of interest
*
* This function is called when @css is about to go away. Here the cgwbs are
* offlined first and only once writeback associated with the blkcg has
* finished do we start step 2 (see above).
*/
static void blkcg_css_offline(struct cgroup_subsys_state *css)
{
/* this prevents anyone from attaching or migrating to this blkcg */
wb_blkcg_offline(css);
/* put the base online pin allowing step 2 to be triggered */
blkcg_unpin_online(css);
}
static void blkcg_css_free(struct cgroup_subsys_state *css)
{
struct blkcg *blkcg = css_to_blkcg(css);
int i;
mutex_lock(&blkcg_pol_mutex);
list_del(&blkcg->all_blkcgs_node);
for (i = 0; i < BLKCG_MAX_POLS; i++)
if (blkcg->cpd[i])
blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
mutex_unlock(&blkcg_pol_mutex);
free_percpu(blkcg->lhead);
kfree(blkcg);
}
static struct cgroup_subsys_state *
blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
{
struct blkcg *blkcg;
int i;
mutex_lock(&blkcg_pol_mutex);
if (!parent_css) {
blkcg = &blkcg_root;
} else {
blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
if (!blkcg)
goto unlock;
}
if (init_blkcg_llists(blkcg))
goto free_blkcg;
for (i = 0; i < BLKCG_MAX_POLS ; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
struct blkcg_policy_data *cpd;
/*
* If the policy hasn't been attached yet, wait for it
* to be attached before doing anything else. Otherwise,
* check if the policy requires any specific per-cgroup
* data: if it does, allocate and initialize it.
*/
if (!pol || !pol->cpd_alloc_fn)
continue;
cpd = pol->cpd_alloc_fn(GFP_KERNEL);
if (!cpd)
goto free_pd_blkcg;
blkcg->cpd[i] = cpd;
cpd->blkcg = blkcg;
cpd->plid = i;
}
spin_lock_init(&blkcg->lock);
refcount_set(&blkcg->online_pin, 1);
INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
INIT_HLIST_HEAD(&blkcg->blkg_list);
#ifdef CONFIG_CGROUP_WRITEBACK
INIT_LIST_HEAD(&blkcg->cgwb_list);
#endif
list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
mutex_unlock(&blkcg_pol_mutex);
return &blkcg->css;
free_pd_blkcg:
for (i--; i >= 0; i--)
if (blkcg->cpd[i])
blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
free_percpu(blkcg->lhead);
free_blkcg:
if (blkcg != &blkcg_root)
kfree(blkcg);
unlock:
mutex_unlock(&blkcg_pol_mutex);
return ERR_PTR(-ENOMEM);
}
static int blkcg_css_online(struct cgroup_subsys_state *css)
{
struct blkcg *parent = blkcg_parent(css_to_blkcg(css));
/*
* blkcg_pin_online() is used to delay blkcg offline so that blkgs
* don't go offline while cgwbs are still active on them. Pin the
* parent so that offline always happens towards the root.
*/
if (parent)
blkcg_pin_online(&parent->css);
return 0;
}
void blkg_init_queue(struct request_queue *q)
{
INIT_LIST_HEAD(&q->blkg_list);
mutex_init(&q->blkcg_mutex);
}
int blkcg_init_disk(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct blkcg_gq *new_blkg, *blkg;
bool preloaded;
new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL);
if (!new_blkg)
return -ENOMEM;
preloaded = !radix_tree_preload(GFP_KERNEL);
/* Make sure the root blkg exists. */
/* spin_lock_irq can serve as RCU read-side critical section. */
spin_lock_irq(&q->queue_lock);
blkg = blkg_create(&blkcg_root, disk, new_blkg);
if (IS_ERR(blkg))
goto err_unlock;
q->root_blkg = blkg;
spin_unlock_irq(&q->queue_lock);
if (preloaded)
radix_tree_preload_end();
return 0;
err_unlock:
spin_unlock_irq(&q->queue_lock);
if (preloaded)
radix_tree_preload_end();
return PTR_ERR(blkg);
}
void blkcg_exit_disk(struct gendisk *disk)
{
blkg_destroy_all(disk);
blk_throtl_exit(disk);
}
static void blkcg_exit(struct task_struct *tsk)
{
if (tsk->throttle_disk)
put_disk(tsk->throttle_disk);
tsk->throttle_disk = NULL;
}
struct cgroup_subsys io_cgrp_subsys = {
.css_alloc = blkcg_css_alloc,
.css_online = blkcg_css_online,
.css_offline = blkcg_css_offline,
.css_free = blkcg_css_free,
.css_rstat_flush = blkcg_rstat_flush,
.dfl_cftypes = blkcg_files,
.legacy_cftypes = blkcg_legacy_files,
.legacy_name = "blkio",
.exit = blkcg_exit,
#ifdef CONFIG_MEMCG
/*
* This ensures that, if available, memcg is automatically enabled
* together on the default hierarchy so that the owner cgroup can
* be retrieved from writeback pages.
*/
.depends_on = 1 << memory_cgrp_id,
#endif
};
EXPORT_SYMBOL_GPL(io_cgrp_subsys);
/**
* blkcg_activate_policy - activate a blkcg policy on a gendisk
* @disk: gendisk of interest
* @pol: blkcg policy to activate
*
* Activate @pol on @disk. Requires %GFP_KERNEL context. @disk goes through
* bypass mode to populate its blkgs with policy_data for @pol.
*
* Activation happens with @disk bypassed, so nobody would be accessing blkgs
* from IO path. Update of each blkg is protected by both queue and blkcg
* locks so that holding either lock and testing blkcg_policy_enabled() is
* always enough for dereferencing policy data.
*
* The caller is responsible for synchronizing [de]activations and policy
* [un]registerations. Returns 0 on success, -errno on failure.
*/
int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
{
struct request_queue *q = disk->queue;
struct blkg_policy_data *pd_prealloc = NULL;
struct blkcg_gq *blkg, *pinned_blkg = NULL;
int ret;
if (blkcg_policy_enabled(q, pol))
return 0;
/*
* Policy is allowed to be registered without pd_alloc_fn/pd_free_fn,
* for example, ioprio. Such policy will work on blkcg level, not disk
* level, and don't need to be activated.
*/
if (WARN_ON_ONCE(!pol->pd_alloc_fn || !pol->pd_free_fn))
return -EINVAL;
if (queue_is_mq(q))
blk_mq_freeze_queue(q);
retry:
spin_lock_irq(&q->queue_lock);
/* blkg_list is pushed at the head, reverse walk to initialize parents first */
list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
struct blkg_policy_data *pd;
if (blkg->pd[pol->plid])
continue;
/* If prealloc matches, use it; otherwise try GFP_NOWAIT */
if (blkg == pinned_blkg) {
pd = pd_prealloc;
pd_prealloc = NULL;
} else {
pd = pol->pd_alloc_fn(disk, blkg->blkcg,
GFP_NOWAIT | __GFP_NOWARN);
}
if (!pd) {
/*
* GFP_NOWAIT failed. Free the existing one and
* prealloc for @blkg w/ GFP_KERNEL.
*/
if (pinned_blkg)
blkg_put(pinned_blkg);
blkg_get(blkg);
pinned_blkg = blkg;
spin_unlock_irq(&q->queue_lock);
if (pd_prealloc)
pol->pd_free_fn(pd_prealloc);
pd_prealloc = pol->pd_alloc_fn(disk, blkg->blkcg,
GFP_KERNEL);
if (pd_prealloc)
goto retry;
else
goto enomem;
}
spin_lock(&blkg->blkcg->lock);
pd->blkg = blkg;
pd->plid = pol->plid;
blkg->pd[pol->plid] = pd;
if (pol->pd_init_fn)
pol->pd_init_fn(pd);
if (pol->pd_online_fn)
pol->pd_online_fn(pd);
pd->online = true;
spin_unlock(&blkg->blkcg->lock);
}
__set_bit(pol->plid, q->blkcg_pols);
ret = 0;
spin_unlock_irq(&q->queue_lock);
out:
if (queue_is_mq(q))
blk_mq_unfreeze_queue(q);
if (pinned_blkg)
blkg_put(pinned_blkg);
if (pd_prealloc)
pol->pd_free_fn(pd_prealloc);
return ret;
enomem:
/* alloc failed, take down everything */
spin_lock_irq(&q->queue_lock);
list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;
struct blkg_policy_data *pd;
spin_lock(&blkcg->lock);
pd = blkg->pd[pol->plid];
if (pd) {
if (pd->online && pol->pd_offline_fn)
pol->pd_offline_fn(pd);
pd->online = false;
pol->pd_free_fn(pd);
blkg->pd[pol->plid] = NULL;
}
spin_unlock(&blkcg->lock);
}
spin_unlock_irq(&q->queue_lock);
ret = -ENOMEM;
goto out;
}
EXPORT_SYMBOL_GPL(blkcg_activate_policy);
/**
* blkcg_deactivate_policy - deactivate a blkcg policy on a gendisk
* @disk: gendisk of interest
* @pol: blkcg policy to deactivate
*
* Deactivate @pol on @disk. Follows the same synchronization rules as
* blkcg_activate_policy().
*/
void blkcg_deactivate_policy(struct gendisk *disk,
const struct blkcg_policy *pol)
{
struct request_queue *q = disk->queue;
struct blkcg_gq *blkg;
if (!blkcg_policy_enabled(q, pol))
return;
if (queue_is_mq(q))
blk_mq_freeze_queue(q);
mutex_lock(&q->blkcg_mutex);
spin_lock_irq(&q->queue_lock);
__clear_bit(pol->plid, q->blkcg_pols);
list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;
spin_lock(&blkcg->lock);
if (blkg->pd[pol->plid]) {
if (blkg->pd[pol->plid]->online && pol->pd_offline_fn)
pol->pd_offline_fn(blkg->pd[pol->plid]);
pol->pd_free_fn(blkg->pd[pol->plid]);
blkg->pd[pol->plid] = NULL;
}
spin_unlock(&blkcg->lock);
}
spin_unlock_irq(&q->queue_lock);
mutex_unlock(&q->blkcg_mutex);
if (queue_is_mq(q))
blk_mq_unfreeze_queue(q);
}
EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
static void blkcg_free_all_cpd(struct blkcg_policy *pol)
{
struct blkcg *blkcg;
list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
if (blkcg->cpd[pol->plid]) {
pol->cpd_free_fn(blkcg->cpd[pol->plid]);
blkcg->cpd[pol->plid] = NULL;
}
}
}
/**
* blkcg_policy_register - register a blkcg policy
* @pol: blkcg policy to register
*
* Register @pol with blkcg core. Might sleep and @pol may be modified on
* successful registration. Returns 0 on success and -errno on failure.
*/
int blkcg_policy_register(struct blkcg_policy *pol)
{
struct blkcg *blkcg;
int i, ret;
mutex_lock(&blkcg_pol_register_mutex);
mutex_lock(&blkcg_pol_mutex);
/* find an empty slot */
ret = -ENOSPC;
for (i = 0; i < BLKCG_MAX_POLS; i++)
if (!blkcg_policy[i])
break;
if (i >= BLKCG_MAX_POLS) {
pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
goto err_unlock;
}
/*
* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy
* without pd_alloc_fn/pd_free_fn can't be activated.
*/
if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
(!pol->pd_alloc_fn ^ !pol->pd_free_fn))
goto err_unlock;
/* register @pol */
pol->plid = i;
blkcg_policy[pol->plid] = pol;
/* allocate and install cpd's */
if (pol->cpd_alloc_fn) {
list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
struct blkcg_policy_data *cpd;
cpd = pol->cpd_alloc_fn(GFP_KERNEL);
if (!cpd)
goto err_free_cpds;
blkcg->cpd[pol->plid] = cpd;
cpd->blkcg = blkcg;
cpd->plid = pol->plid;
}
}
mutex_unlock(&blkcg_pol_mutex);
/* everything is in place, add intf files for the new policy */
if (pol->dfl_cftypes)
WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
pol->dfl_cftypes));
if (pol->legacy_cftypes)
WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
pol->legacy_cftypes));
mutex_unlock(&blkcg_pol_register_mutex);
return 0;
err_free_cpds:
if (pol->cpd_free_fn)
blkcg_free_all_cpd(pol);
blkcg_policy[pol->plid] = NULL;
err_unlock:
mutex_unlock(&blkcg_pol_mutex);
mutex_unlock(&blkcg_pol_register_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(blkcg_policy_register);
/**
* blkcg_policy_unregister - unregister a blkcg policy
* @pol: blkcg policy to unregister
*
* Undo blkcg_policy_register(@pol). Might sleep.
*/
void blkcg_policy_unregister(struct blkcg_policy *pol)
{
mutex_lock(&blkcg_pol_register_mutex);
if (WARN_ON(blkcg_policy[pol->plid] != pol))
goto out_unlock;
/* kill the intf files first */
if (pol->dfl_cftypes)
cgroup_rm_cftypes(pol->dfl_cftypes);
if (pol->legacy_cftypes)
cgroup_rm_cftypes(pol->legacy_cftypes);
/* remove cpds and unregister */
mutex_lock(&blkcg_pol_mutex);
if (pol->cpd_free_fn)
blkcg_free_all_cpd(pol);
blkcg_policy[pol->plid] = NULL;
mutex_unlock(&blkcg_pol_mutex);
out_unlock:
mutex_unlock(&blkcg_pol_register_mutex);
}
EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
/*
* Scale the accumulated delay based on how long it has been since we updated
* the delay. We only call this when we are adding delay, in case it's been a
* while since we added delay, and when we are checking to see if we need to
* delay a task, to account for any delays that may have occurred.
*/
static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
{
u64 old = atomic64_read(&blkg->delay_start);
/* negative use_delay means no scaling, see blkcg_set_delay() */
if (atomic_read(&blkg->use_delay) < 0)
return;
/*
* We only want to scale down every second. The idea here is that we
* want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
* time window. We only want to throttle tasks for recent delay that
* has occurred, in 1 second time windows since that's the maximum
* things can be throttled. We save the current delay window in
* blkg->last_delay so we know what amount is still left to be charged
* to the blkg from this point onward. blkg->last_use keeps track of
* the use_delay counter. The idea is if we're unthrottling the blkg we
* are ok with whatever is happening now, and we can take away more of
* the accumulated delay as we've already throttled enough that
* everybody is happy with their IO latencies.
*/
if (time_before64(old + NSEC_PER_SEC, now) &&
atomic64_try_cmpxchg(&blkg->delay_start, &old, now)) {
u64 cur = atomic64_read(&blkg->delay_nsec);
u64 sub = min_t(u64, blkg->last_delay, now - old);
int cur_use = atomic_read(&blkg->use_delay);
/*
* We've been unthrottled, subtract a larger chunk of our
* accumulated delay.
*/
if (cur_use < blkg->last_use)
sub = max_t(u64, sub, blkg->last_delay >> 1);
/*
* This shouldn't happen, but handle it anyway. Our delay_nsec
* should only ever be growing except here where we subtract out
* min(last_delay, 1 second), but lord knows bugs happen and I'd
* rather not end up with negative numbers.
*/
if (unlikely(cur < sub)) {
atomic64_set(&blkg->delay_nsec, 0);
blkg->last_delay = 0;
} else {
atomic64_sub(sub, &blkg->delay_nsec);
blkg->last_delay = cur - sub;
}
blkg->last_use = cur_use;
}
}
/*
* This is called when we want to actually walk up the hierarchy and check to
* see if we need to throttle, and then actually throttle if there is some
* accumulated delay. This should only be called upon return to user space so
* we're not holding some lock that would induce a priority inversion.
*/
static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
{
unsigned long pflags;
bool clamp;
u64 now = blk_time_get_ns();
u64 exp;
u64 delay_nsec = 0;
int tok;
while (blkg->parent) {
int use_delay = atomic_read(&blkg->use_delay);
if (use_delay) {
u64 this_delay;
blkcg_scale_delay(blkg, now);
this_delay = atomic64_read(&blkg->delay_nsec);
if (this_delay > delay_nsec) {
delay_nsec = this_delay;
clamp = use_delay > 0;
}
}
blkg = blkg->parent;
}
if (!delay_nsec)
return;
/*
* Let's not sleep for all eternity if we've amassed a huge delay.
* Swapping or metadata IO can accumulate 10's of seconds worth of
* delay, and we want userspace to be able to do _something_ so cap the
* delays at 0.25s. If there's 10's of seconds worth of delay then the
* tasks will be delayed for 0.25 second for every syscall. If
* blkcg_set_delay() was used as indicated by negative use_delay, the
* caller is responsible for regulating the range.
*/
if (clamp)
delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
if (use_memdelay)
psi_memstall_enter(&pflags);
exp = ktime_add_ns(now, delay_nsec);
tok = io_schedule_prepare();
do {
__set_current_state(TASK_KILLABLE);
if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS))
break;
} while (!fatal_signal_pending(current));
io_schedule_finish(tok);
if (use_memdelay)
psi_memstall_leave(&pflags);
}
/**
* blkcg_maybe_throttle_current - throttle the current task if it has been marked
*
* This is only called if we've been marked with set_notify_resume(). Obviously
* we can be set_notify_resume() for reasons other than blkcg throttling, so we
* check to see if current->throttle_disk is set and if not this doesn't do
* anything. This should only ever be called by the resume code, it's not meant
* to be called by people willy-nilly as it will actually do the work to
* throttle the task if it is setup for throttling.
*/
void blkcg_maybe_throttle_current(void)
{
struct gendisk *disk = current->throttle_disk;
struct blkcg *blkcg;
struct blkcg_gq *blkg;
bool use_memdelay = current->use_memdelay;
if (!disk)
return;
current->throttle_disk = NULL;
current->use_memdelay = false;
rcu_read_lock();
blkcg = css_to_blkcg(blkcg_css());
if (!blkcg)
goto out;
blkg = blkg_lookup(blkcg, disk->queue);
if (!blkg)
goto out;
if (!blkg_tryget(blkg))
goto out;
rcu_read_unlock();
blkcg_maybe_throttle_blkg(blkg, use_memdelay);
blkg_put(blkg);
put_disk(disk);
return;
out:
rcu_read_unlock();
}
/**
* blkcg_schedule_throttle - this task needs to check for throttling
* @disk: disk to throttle
* @use_memdelay: do we charge this to memory delay for PSI
*
* This is called by the IO controller when we know there's delay accumulated
* for the blkg for this task. We do not pass the blkg because there are places
* we call this that may not have that information, the swapping code for
* instance will only have a block_device at that point. This set's the
* notify_resume for the task to check and see if it requires throttling before
* returning to user space.
*
* We will only schedule once per syscall. You can call this over and over
* again and it will only do the check once upon return to user space, and only
* throttle once. If the task needs to be throttled again it'll need to be
* re-set at the next time we see the task.
*/
void blkcg_schedule_throttle(struct gendisk *disk, bool use_memdelay)
{
if (unlikely(current->flags & PF_KTHREAD))
return;
if (current->throttle_disk != disk) {
if (test_bit(GD_DEAD, &disk->state))
return;
get_device(disk_to_dev(disk));
if (current->throttle_disk)
put_disk(current->throttle_disk);
current->throttle_disk = disk;
}
if (use_memdelay)
current->use_memdelay = use_memdelay;
set_notify_resume(current);
}
/**
* blkcg_add_delay - add delay to this blkg
* @blkg: blkg of interest
* @now: the current time in nanoseconds
* @delta: how many nanoseconds of delay to add
*
* Charge @delta to the blkg's current delay accumulation. This is used to
* throttle tasks if an IO controller thinks we need more throttling.
*/
void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
{
if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
return;
blkcg_scale_delay(blkg, now);
atomic64_add(delta, &blkg->delay_nsec);
}
/**
* blkg_tryget_closest - try and get a blkg ref on the closet blkg
* @bio: target bio
* @css: target css
*
* As the failure mode here is to walk up the blkg tree, this ensure that the
* blkg->parent pointers are always valid. This returns the blkg that it ended
* up taking a reference on or %NULL if no reference was taken.
*/
static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
struct cgroup_subsys_state *css)
{
struct blkcg_gq *blkg, *ret_blkg = NULL;
rcu_read_lock();
blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_bdev->bd_disk);
while (blkg) {
if (blkg_tryget(blkg)) {
ret_blkg = blkg;
break;
}
blkg = blkg->parent;
}
rcu_read_unlock();
return ret_blkg;
}
/**
* bio_associate_blkg_from_css - associate a bio with a specified css
* @bio: target bio
* @css: target css
*
* Associate @bio with the blkg found by combining the css's blkg and the
* request_queue of the @bio. An association failure is handled by walking up
* the blkg tree. Therefore, the blkg associated can be anything between @blkg
* and q->root_blkg. This situation only happens when a cgroup is dying and
* then the remaining bios will spill to the closest alive blkg.
*
* A reference will be taken on the blkg and will be released when @bio is
* freed.
*/
void bio_associate_blkg_from_css(struct bio *bio,
struct cgroup_subsys_state *css)
{
if (bio->bi_blkg)
blkg_put(bio->bi_blkg);
if (css && css->parent) {
bio->bi_blkg = blkg_tryget_closest(bio, css);
} else {
blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg);
bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg;
}
}
EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
/**
* bio_associate_blkg - associate a bio with a blkg
* @bio: target bio
*
* Associate @bio with the blkg found from the bio's css and request_queue.
* If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is
* already associated, the css is reused and association redone as the
* request_queue may have changed.
*/
void bio_associate_blkg(struct bio *bio)
{
struct cgroup_subsys_state *css;
if (blk_op_is_passthrough(bio->bi_opf))
return;
rcu_read_lock();
if (bio->bi_blkg)
css = bio_blkcg_css(bio);
else
css = blkcg_css();
bio_associate_blkg_from_css(bio, css);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(bio_associate_blkg);
/**
* bio_clone_blkg_association - clone blkg association from src to dst bio
* @dst: destination bio
* @src: source bio
*/
void bio_clone_blkg_association(struct bio *dst, struct bio *src)
{
if (src->bi_blkg)
bio_associate_blkg_from_css(dst, bio_blkcg_css(src));
}
EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
static int blk_cgroup_io_type(struct bio *bio)
{
if (op_is_discard(bio->bi_opf))
return BLKG_IOSTAT_DISCARD;
if (op_is_write(bio->bi_opf))
return BLKG_IOSTAT_WRITE;
return BLKG_IOSTAT_READ;
}
void blk_cgroup_bio_start(struct bio *bio)
{
struct blkcg *blkcg = bio->bi_blkg->blkcg;
int rwd = blk_cgroup_io_type(bio), cpu;
struct blkg_iostat_set *bis;
unsigned long flags;
if (!cgroup_subsys_on_dfl(io_cgrp_subsys))
return;
/* Root-level stats are sourced from system-wide IO stats */
if (!cgroup_parent(blkcg->css.cgroup))
return;
cpu = get_cpu();
bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
flags = u64_stats_update_begin_irqsave(&bis->sync);
/*
* If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
* bio and we would have already accounted for the size of the bio.
*/
if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
bio_set_flag(bio, BIO_CGROUP_ACCT);
bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
}
bis->cur.ios[rwd]++;
/*
* If the iostat_cpu isn't in a lockless list, put it into the
* list to indicate that a stat update is pending.
*/
if (!READ_ONCE(bis->lqueued)) {
struct llist_head *lhead = this_cpu_ptr(blkcg->lhead);
llist_add(&bis->lnode, lhead);
WRITE_ONCE(bis->lqueued, true);
}
u64_stats_update_end_irqrestore(&bis->sync, flags);
cgroup_rstat_updated(blkcg->css.cgroup, cpu);
put_cpu();
}
bool blk_cgroup_congested(void)
{
struct blkcg *blkcg;
bool ret = false;
rcu_read_lock();
for (blkcg = css_to_blkcg(blkcg_css()); blkcg;
blkcg = blkcg_parent(blkcg)) {
if (atomic_read(&blkcg->congestion_count)) {
ret = true;
break;
}
}
rcu_read_unlock();
return ret;
}
module_param(blkcg_debug_stats, bool, 0644);
MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");
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